Composition and process for enhancing controlled free radical polymerization

ABSTRACT

The present invention relates to a composition and process for enhancing the controlled radical polymerization in the presence of nitroxyls and nitroxylethers by adding a chain transfer agent selected from the group consisting of mercaptanes, thioethers and disulfides to the polymerizable mixture. A further subject of the invention is the use of mercaptanes, thioethers and disulfides for increasing rate and yield of controlled radical polymerizations in the presence of a nitroxyl or a nitroxylether.

[0001] The present invention relates to a composition and process forenhancing the controlled radical polymerization in the presence ofnitroxyls and nitroxylethers by adding a chain transfer agent selectedfrom the group consisting of mercaptanes, thioethers and disulfides tothe polymerizable mixture.

[0002] U.S. Pat. No. 4,581,429 to Solomon et al., issued Apr. 8, 1986,discloses a free radical polymerization process which controls thegrowth of polymer chains to produce short chain or oligomerichomopolymers and copolymers, including block and graft copolymers. Thistype of polymerization is frequently called “living polymerization”. Theprocess employs an initiator having the formula (in part) R′R″N—O—X,where X is a free radical species capable of polymerizing unsaturatedmonomers. The reactions typically have low conversion rates.Specifically mentioned radical R′R″N—O. groups are derived from 1,1,3,3tetraethylisoindoline, 1,1,3,3 tetrapropylisoindoline, 2,2,6,6tetramethylpiperidine, 2,2,5,5 tetramethyl-pyrrolidine ordi-t-butylamine.

[0003] U.S. Pat. No. 5,322,912 to Georges et al. issued Jun. 21, 1994discloses a polymerization process using a free radical initiator, apolymerizable monomer compound and a stable free radical agent of thebasic structure R′R″N—O. for the synthesis of homopolymers and blockcopolymers.

[0004] EP 0,759,039 to Georges et al. describes the improvedpolymerization of acrylates using4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxy free radical as stable freeradical agent R′R″N—O..

[0005] However, the suggested compounds do not fulfill all requirements.Particularly the polymerization of acrylates does not proceed fastenough and/or the monomer to polymer conversion is not as high asdesired.

[0006] For this reason many attempts have been made in the last years toimprove conversion rate whilst retaining the advantages of controlledpolymerization such as for example low polydispersity and the capabilityof block copolymer formation. Many improvements have been made bymodifying the chemical structure of the nitroxyl radical or of thenitroxyl ether.

[0007] WO 98/13392 for example describes open chain alkoxyaminecompounds which have a symmetrical substitution pattern and are derivedfrom NO gas or from nitroso compounds.

[0008] WO 96/24620 describes a polymerization process in which veryspecific stable free radical agents are used, such as for example

[0009] WO 98/30601 discloses specific nitroxyls based onimidazolidinons.

[0010] WO 98/44008 discloses specific nitroxyls based on morpholinones,piperazinones and piperazindiones.

[0011] Despite the above mentioned structural attempts to improvecontrolled radical polymerization reactions there is still a need forimproving the polymerization process to obtain higher yields in shorterreaction times.

[0012] EP-A-735 052 for example discloses a method for preparingthermoplastic polymers of narrow polydispersitiy by freeradical-initated polymerization, which comprises adding a free radicalinitiator, a stable free radical agent and a pyridinium tosylate to astyrene monomer, which enhances the reaction time and conversion rate ofthe polymerization.

[0013] Other accelerators such as phosphonic and sulfonic acids aredescribed in WO 96/18663, phosphites are described in U.S. Pat. No.5,610,249 and protonic acids are described in U.S. Pat. No. 5,322,912.

[0014] Surprisingly it has now been found that the rate ofpolymerization and conversion can be strongly improved by adding to thepolymerizable mixture a chain transfer agent selected from the groupconsisting of a mercaptane, a thioether or a disulfide. Higher molecularweights are reached in shorter reaction times whilst polydispersityremains low and surprisingly the polymers can be completely reinitiatedto form block copolymers. This is surprising, since one would expectthat at least partially terminated polymers (not anymore “living”polymers) are formed.

[0015] Moreover when reinitiating a polymer, which has been prepared viacontrolled radical polymerization in the presence of a nitroxyl radicalor a nitroxylether, to form block copolymers also a remarkable increasein rate and conversion of block copolymer formation is observed whensaid chain transfer agents are added to the block copolymerization step.

[0016] The low polydispersity which is characteristic for controlledradical polymerizations remains essentially unaffected by the additionof said chain transfer agents.

[0017] The polymerization processes and resin products of the presentinvention are useful in many applications, including a variety ofspecialty applications, such as for the preparation of block copolymersand/or graft copolymers which are useful as compatibilizing agents forpolymer blends or dispersing agents for coating systems.

[0018] Polymers prepared by nitroxyl radical or nitroxyl ether mediatedradical polymerization exhibit sometimes a yellow/brown color.Surprisingly it has been found that the presence of the chain transferagent in the polymerizable composition is in many cases also beneficialfor the color of the final polymer.

[0019] One subject of the present invention is a polymerizablecomposition, comprising

[0020] a) at least one ethylenically unsaturated monomer or oligomer,and

[0021] b1) at least one nitroxylether having the structural element

[0022] wherein

[0023] X represents a group having at least one carbon atom and is suchthat the free radical X. derived from X is capable of initiatingpolymerization of ethylenically unsaturated monomers; or

[0024] b2) at least one stable free nitroxyl radical

[0025] and a free radical initiator and

[0026] c) a chain transfer agent selected from the group consisting of amercaptane, a thioether and a disulfide, with the proviso, that, if astable free nitroxyl radical is present, the chain transfer ag nt is nota disulfide.

[0027] Also subject of the invention is a polymerizable composition,comprising

[0028] a) a macroinitiator, which is a oligomer or polymer prepared inthe presence of a nitroxyl radical or a nitroxylether and havingattached to the oligomer/polymer backbone a nitroxyl group with thestructural element

[0029] b) an ethylenically unsaturated monomer or oligomer and

[0030] c) a chain transfer agent selected from the group consisting of amercaptane, a thioether and a disulfide.

[0031] The macroinitiator can be prepared by polymerizing a monomer inthe presence of a nitroxyl or nitroxylether or by grafting of anexisting conventionally polymerized polymer with a nitroxylether or anitroxyl radical, as described in EP-A-1 115 766 or EP-A-1 115 765.

[0032] An ethylenically unsaturated oligomer is for example apoloyethylenglykoldiacrylate or in general a oligomer which has beenfunctionalized at the end groups. Such oligomers are known and largelyitems of commerce.

[0033] Preferably the ethylenically unsaturated monomer is selected fromthe group consisting of ethylene, propylene, n-butylene, i-butylene,styrene, substituted styrene, conjugated dienes, acrolein, vinylacetate, vinylpyrrolidone, vinylimidazole, maleic anhydride,(alkyl)acrylic acidanhydrides, (alkyl)acrylic acid salts, (alkyl)acrylicesters, (alkyl)acrylonitriles, (alkyl)acrylamides, vinyl halides orvinylidene halides.

[0034] Preferably the ethylenically unsaturated monomer is a compound offormula CH₂═C(R_(a))—(C═Z)—R_(b), wherein R_(a) is hydrogen orC₁-C₄alkyl, R_(b) is NH₂, O⁻(Me⁺), glycidyl, unsubstituted C₁-C₁₈alkoxy,C₂-C₁₀₀alkoxy interrupted by at least one N and/or O atom, orhydroxy-substituted C₁-C₁₈alkoxy, unsubstituted C₁-C₁₈alkylamino,di(C₁-C₁₈alkyl)amino, hydroxy-substituted C₁-C₁₈alkylamino orhydroxy-substituted di(C₁-C₁₈alkyl)amino, —O—CH₂—CH₂—N(CH₃)₂ or—O—CH₂—CH₂—N⁺H(CH₃)₂ An⁻;

[0035] An⁻ is a anion of a monovalent organic or inorganic acid;

[0036] Me is a monovalent metal atom or the ammonium ion.

[0037] Z is oxygen or sulfur.

[0038] Examples of acids from which the anion An⁻ is derived areC₁-C₁₂carboxylic acids, organic sulfonic acids such as CF₃SO₃H orCH₃SO₃H, mineralic acids such as HCl, HBr or Hl, oxo acids such as HClO₄or complex acids such as HPF₆ or HBF₄.

[0039] Examples for R_(a) as C₂-C₁₀₀alkoxy interrupted by at least one Oatom are of formula

[0040] wherein R_(c) is C₁-C₂₅alkyl, phenyl or phenyl substituted byC₁-C₁₈alkyl, R_(d) is hydrogen or methyl and v is a number from 1 to 50.These monomers are for example derived from non ionic surfactants byacrylation of the corresponding alkoxylated alcohols or phenols. Therepeating units may be derived from ethylene oxide, propylene oxide ormixtures of both.

[0041] Further examples of suitable acrylate or methacrylate monomersare given below.

[0042] An⁻, wherein An⁻ and R_(a) have the meaning as defined above andR_(e) is methyl or benzyl. An ⁻ is preferably Cl⁻, Br⁻ or ⁻O₃S—CH₃.

[0043] Examples for suitable monomers other than acrylates are

[0044] Preferably R_(a) is hydrogen or methyl, R_(b) is NH₂, gycidyl,unsubstituted or with hydroxy substituted C₁-C₄alkoxy, unsubstitutedC₁-C₄alkylamino, di(C₁-C₄alkyl)amino, hydroxy-substitutedC₁-C₄alkylamino or hydroxy-substituted di(C₁-C₄alkyl)amino;and

[0045] Z is oxygen.

[0046] More preferred the ethylenically unsaturated monomer is anacrylic acid ester, acrylamide, acryinitrile, methacrylic acid ester,methacrylamide, methacryinitrile.

[0047] Acrylic acid esters and methacrylic acid esters are typicallyC₁-C₁₈alkyl esters.

[0048] Most preferred is n-butylacrylate, tert-butylacrylate,methylacrylate, ethylacrylate, propylacrylate, hexylacrylate andhydroxyethylacrylate.

[0049] The nitroxylethers and nitroxyl radicals are principally knownfrom U.S. Pat. No. 4,581,429 or EP-A-621 878. Particularly useful arethe open chain compounds described in WO 98/13392, WO 99/03894 and WO00/07981, the piperidine derivatives described in WO 99/67298 and GB2335190 or the heterocyclic compounds described in GB 2342649 and WO96/24620. Preferably the nitroxylether of component b1) is of formula A,B or O,

[0050] wherein

[0051] m is 1,

[0052] R is hydrogen, C₁-C₁₈alkyl which is uninterrupted or interruptedby one or more oxygen atoms, cyanoethyl, benzoyl, glycidyl, a monovalentradical of an aliphatic carboxylic acid having 2 to 18 carbon atoms, ofa cycloaliphatic carboxylic acid having 7 to 15 carbon atoms, or anα,β-unsaturated carboxylic acid having 3 to 5 carbon atoms or of anaromatic carboxylic acid having 7 to 15 carbon atoms;

[0053] p is 1;

[0054] R₁₀₁ is C₁-C₁₂alkyl, C₅-C₇cycloalkyl, C₇-C₈aralkyl,C₂-C₁₈alkanoyl, C₃-C₅alkenoyl or benzoyl;

[0055] R₁₀₂ is C₁-C₁₈alkyl, C₅-C₇cycloalkyl, C₂-C₈alkenyl unsubstitutedor substituted by a cyano, carbonyl or carbamide group, or is glycidyl,a group of the formula —CH₂CH(OH)—Z or of the formula —CO—Z or —CONH—Zwherein Z is hydrogen, methyl or phenyl;

[0056] G₆ is hydrogen and G₅ is hydrogen or C₁-C₄alkyl,

[0057] G₁ and G₃ are methyl and G₂ and G₄ are ethyl or propyl or G₁ andG₂ are methyl and G₃ and

[0058] G₄ are ethyl or propyl; and

[0059] X is selected from the group consisting of —CH₂-phenyl,CH₃CH-phenyl, (CH₃)₂C-phenyl, (C₅-₆cycloalkyl)₂CCN, (CH₃)₂CCN,—CH₂CH═CH₂, CH₃CH—CH═CH₂ (C₁-C₄alkyl)CR₂₀—C(O)-phenyl,(C₁-C₄)alkyl-CR₂₀—C(O)—(C₁-C₄)alkoxy,(C₁-C₄)alkyl-CR₂₀—C(O)—(C₁-C₄)alkyl,(C₁-C₄)alkyl-CR₂₀—C(O)-N-di(C₁-C₄)alkyl,(C₁-C₄alky-CR₂₀-C(O)—NH(C₁-C₄)alkyl, (C₁-C₄)alkyl-CR₂₀—C(O)—NH₂, wherein

[0060] R₂₀ is hydrogen or (C₁-C₄)alkyl.

[0061] More preferably in formula A, B and O

[0062] R is hydrogen, C₁-C₁₈alkyl, cyanoethyl, benzoyl, glycidyl, amonovalent radical of an aliphatic, carboxylic acid;

[0063] R₁₀₁ is C₁-C₁₂alkyl, C₇-C₈aralkyl, C₂-C₁₈alkanoyl, C₃-C₅alkenoylor benzoyl;

[0064] R₁₀₂ is C₁-C₁₈alkyl, glycidyl, a group of the formula—CH₂CH(OH)—Z or of the formula —CO—Z, wherein Z is hydrogen, methyl orphenyl; and

[0065] X is CH₃—CH-phenyl.

[0066] The above compounds and their preparation are described in GB2335190.

[0067] Another preferred group of nitroxylethers of component b1) arethose of formula (Ic), (Id), (Ie), (If), (Ig) or (Ih)

[0068] wherein R₁, R₂, R₃ and R₄ independently of each other areC₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinyl, C₁-C₁₈alkyl, C₃-C₁₈alkenyl,C₃-C₁₈alkinyl which are substituted by OH, halogen or a group—O—C(O)—R₅, C₂-C₁₈alkyl which is interrupted by at least one O atomand/or NR₅ group, C₃-C₁₂cycloalkyl or C₆-C₁₀aryl or R₁ and R₂ andior R₃and R₄ together with the linking carbon atom form a C₃-C₁₂cycloalkylradical;

[0069] R₅, R₆ and R₇ independently are hydrogen, C₁-C₁₈alkyl orC₆-C₁₀aryl;

[0070] R₈ is hydrogen, OH, C₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinyl,C₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinyl which are substituted by oneor more OH, halogen or a group —O—C(O)—R₅, C₂-C₁₈alkyl which isinterrupted by at least one O atom and/or NR₅ group, C₃-C₁₂cycloalkyl orC₆-C₁₀aryl, C₇-C₉phenylalkyl, C₅-C₁₀heteroaryl, —C(O)—C₁-C₁₈alkyl,—O—C₁-C₁₈alkyl or —COOC₁-C₁₈alkyl;

[0071] R₉, R₁₀, R₁₁ and R₁₂ are independently hydrogen, phenyl orC₁-C₁₈alkyl; and

[0072] X is selected from the group consisting of —CH₂-phenyl,CH₃CH-phenyl, (CH₃)₂C-phenyl, (C₅-C₆cycloalkyl)₂CCN, (CH₃)₂CCN,—CH₂CH═CH₂, CH₃CH—CH═CH₂ (C₁-C₄alkyl)CR₂₀—C(O)-phenyl,(C₁-C₄)alkyl-CR₂₀—C(O)—(C_(1-C) ₄)alkoxy,(C₁-C₄)alkyl-CR₂₀—C(O)—(C₁-C₄)alkyl,(C₁-C₄)alkyl-CR₂₀—C(O)—N-di(C₁-C₄)alkyl,(C₁-C₄)alkyl-CR₂₀—C(O)—NH(C₁-C₄)alkyl, (C₁-C₄)alkyl-CR₂₀—C(O)—NH₂,wherein

[0073] R₂₀ is hydrogen or (C₁-C₄)alkyl.

[0074] More preferably in formula (Ic), (Id), (Ie), (f), (Ig) and (Ih)at least two of R₁, R₂, R₃ and R₄ are thyl, propyl or butyl and theremaining are methyl; or

[0075] R₁ and R₂ or R₃ and R₄ together with the linking carbon atom forma C₅-C₆cycloalkyl radical and one of the remaining substituents isethyl, propyl or butyl.

[0076] Most preferably X is CH₃CH-phenyl.

[0077] The above compounds and their preparation is described in GB2342649.

[0078] When a nitroxyl radical is used together with a free radicalinitiator, the nitroxyl radical of component b2) is preferably offormula A′, B′ or O′,

[0079] wherein

[0080] m is 1,

[0081] R is hydrogen, C₁-C₁₈alkyl which is uninterrupted or interruptedby one or more oxygen atoms, cyanoethyl, benzoyl, glycidyl, a monovalentradical of an aliphatic carboxylic acid having 2 to 18 carbon atoms, ofa cycloaliphatic carboxylic acid having 7 to 15 carbon atoms, or anα,β-unsaturat d carboxylic acid having 3 to 5 carbon atoms or of anaromatic carboxylic acid having 7 to 15 carbon atoms;

[0082] p is 1;

[0083] R₁ is C₁-C₁₂alkyl, C₅-C₇cycloalkyl, C₇-C₈aralkyl, C₂-C₁₈alkanoyl,C₃-C₅alk noyl or benzoyl

[0084] R₂ is C₁-C₁₈alkyl, C₅-C₇cycloalkyl, C₂-C₈alkenyl unsubstituted orsubstituted by a cyano, carbonyl or carbamide group, or is glycidyl, agroup of the formula —CH₂CH(OH)—Z or of the formula —CO—Z or —CONH—Zwherein Z is hydrogen, methyl or phenyl;

[0085] G₆ is hydrogen and G₅ is hydrogen or C₁-C₄alkyl, and

[0086] G₁ and G₃ are methyl and G₂ and G₄ are ethyl or propyl or G₁ andG₂ are methyl and G₃ and

[0087] G₄ are ethyl or propyl.

[0088] More preferably in formula A′, B′ and O′

[0089] R is hydrogen, C₁-C₁₈alkyl, cyanoethyl, benzoyl, glycidyl, amonovalent radical of an aliphatic, carboxylic acid;

[0090] R₁ is C₁-C₁₂alkyl, C₇-C₈aralkyl, C₂-C₁₈alkanoyl, C₃-C₅alkenoyl orbenzoyl;

[0091] R₂ is C₁-C₁₈alkyl, glycidyl, a group of the formula —CH₂CH(OH)—Zor of the formula —CO—Z, wherein Z is hydrogen, methyl or phenyl.

[0092] The above compounds and their preparation are described in GB2335190.

[0093] Another preferred group of nitroxyl radicals are those of formula(Ic′), (Id′), (Ie′), (If′), (Ig′) or (Ih′)

[0094] wherein R₁, R₂, R₃ and R₄ independently of each other areC₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinyl, C₁-C₁₈alkyl, C₃-C₁₈alkenyl,C₃-C₁₈alkinyl which are substituted by OH, halogen or a group—O—C(O)—R₅, C₂-C₁₈alkyl which is interrupted by at least one O atomand/or NR₅ group, C₃-C₁₂cycloalkyl or C₆-C₁₀aryl or R₁ and R₂ and/or R₃and R₄ together with the linking carbon atom form a C₃-C₁₂cycloalkylradical;

[0095] R₅, R₆ and R₇ independently are hydrogen, C₁-C₁₈alkyl orC₆-C₁₀aryl;

[0096] R₈ is hydrogen, OH, C₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinyl,C₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinyl which are substituted by oneor more OH, halogen or a group —O—C(O)—R₅, C₂-C₁₈alkyl which isinterrupted by at least one O atom and/or NR₅ group, C₃-C₁₂cycloalkyl orC₆-C₁₀aryl, C₇-C₉phenylalkyl, C₅-C₁₀heteroaryl, —C(O)—C₁-C₁₈alkyl,—O—C₁-C₁₈alkyl or —COOC₁-C₁₈alkyl; and

[0097] R₉, R₁₀, R₁₁ and R₁₂ are independently hydrogen, phenyl orC₁-C₁₈alkyl.

[0098] More preferably in formula (Ic′), (Id′), (Ie′), (If′), (Ig′) and(Ih′) at least two of R₁, R₂, R₃ and R₄ are ethyl, propyl or butyl andthe remaining are methyl; or

[0099] R₁ and R₂ or R₃ and R₄ together with the linking carbon atom forma C₅-C₆cycloalkyl radical and one of the remaining substituents isethyl, propyl or butyl.

[0100] The above compounds and their preparation is described in GB2342649.

[0101] The structural element

[0102] attached to the polymer backbone of the macroinitiator ispreferably derived from a compound of formulae A, B, O (A′, B′, O′) orof formulae Ic, Id, Ie, If, Ig, Ih (Ic′, Id′, Ie′, If′, Ig′, Ih′).

[0103] Further preferences given above for the nitroxyl ether andnitroxyl radical apply also for the nitroxyl moiety attached to thepolymer backbone of the macroinitiator.

[0104] The alkyl radicals in the various substituents may be linear orbranched. Examples of alkyl containing 1 to 18 carbon atoms are methyl,ethyl, propyl, isopropyl, butyl, 2-butyl, isobutyl, t-butyl, pentyl,2-pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, t-octyl, nonyl, decyl,undecyl, dodecyl, tridecyl, tetradecyl, hexadecyl and octadecyl.

[0105] Alkenyl with 3 to 18 carbon atoms is a linear or branched radicalas for example propenyl, 2-butenyl, 3-butenyl, isobutenyl,n-2,4-pentadienyl, 3-methyl-2-butenyl, n-2-octenyl, n-2-dodecenyl,iso-dodecenyl, oleyl, n-2-octadecenyl oder n4-octadecenyl. Preferred isalkenyl with 3 bis 12, particularly preferred with 3 to 6 carbon atoms.

[0106] Alkinyl with 3 to 18 is a linear or branched radical as forexample propinyl (—CH₂—C≡CH ), 2-butinyl, 3-butinyl, n-2-octinyl, odern-2-octadecinyl. Preferred is alkinyl with 3 to 12, particularlypreferred with 3 to 6 carbon atoms.

[0107] Examples for hydroxy substituted alkyl are hydroxy propyl,hydroxy butyl or hydroxy hexyl.

[0108] Examples for halogen substituted alkyl are dichloropropyl,monobromobutyl or trichlorohexyl.

[0109] C₂-C₁₈alkyl interrupted by at least one O atom is for example—CH₂—CH₂—O—CH₂—CH₃, —CH₂—CH₂—O—CH₃— or—CH₂—CH₂—O—CH₂—CH₂—CH₂—O—CH₂—CH₃—. It is preferably derived frompolyethlene glycol. A general description is —((CH₂)_(a)—O)_(b)—H/CH₃,wherein a is a number from 1 to 6 and b is a number from 2 to 10.

[0110] C₂-C₁₈alkyl interrupted by at least one NR₅ group may begenerally described as —((CH₂)_(a)—NR₅)_(b)—H/CH₃, wherein a, b and R₅are as defined above.

[0111] C3-C₁₂cycloalkyl is typically, cyclopropyl, cyclopentyl,methylcyclopentyl, dimethylcyclopentyl, cyclohexyl, methylcyclohexyl ortrimethylcyclohexyl.

[0112] C₆C₁₀ aryl is for example phenyl or naphthyl, but also comprisedare C₁-C₄alkyl substituted phenyl, C₁-C₄alkoxy substituted phenyl,hydroxy, halogen or nitro substituted phenyl. Examples for alkylsubstituted phenyl are ethylbenzene, toluene, xylene and its isomers,mesitylene or isopropylbenzene. Halogen substituted phenyl is forexample dichlorobenzene or bromotoluene.

[0113] Alkoxy substituents are typically methoxy, ethoxy, propoxy orbutoxy and their corresponding isomers.

[0114] C₇-C₉phenylalkyl is benzyl, phenylethyl or phenylpropyl.

[0115] C₅-C₁₀heteroaryl is for example pyrrol, pyrazol, imidazol, 2, 4,dimethylpyrrol, 1-methylpyrrol, thiophene, furane, furfural, indol,cumarone, oxazol, thiazol, isoxazol, isothiazol, triazol, pyridine,α-picoline, pyridazine, pyrazine or pyrimidine.

[0116] If R is a monovalent radical of a carboxylic acid, it is, forexample, an acetyl, propionyl, butyryl, valeroyl, caproyl, stearoyl,lauroyl, acryloyl, methacryloyl, benzoyl, cinnamoyl orβ-(3,5di-tert-butyl-4-hydroxyphenyl)propionyl radical.

[0117] C₁-C₁₈alkanoyl is for example, formyl, propionyl, butyryl,octanoyl, dodecanoyl but preferably acetyl and C₃-C₅alkenoyl is inparticular acryloyl.

[0118] Particularly suitable nitroxylethers and nitroxyl radicals arethose of formulae

[0119] The free radical initiator of component b2) is preferably abis-azo compound, a peroxide perester or a hydroperoxide.

[0120] Specific preferred radical sources are2,2′-azobisisobutyronitrile, 2,2′-azobis(2-methyl-butyronitrile),2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobis(4-methoxy-2,4dimethylvaleronitrile),1,1′-azobis(1-cyclohexanecarbonitrile), 2,2′-azobis(isobutyramide)dihydrate, 2-phenylazo-2,4dimethyl-4-methoxyvaleronitrile,dimethyl-2,2′-azobisisobutyrate, 2-(carbamoylazo)isobutyronitrile,2,2′-azobis(2,4,4-trimethylpentane), 2,2′-azobis(2-methylpropane),2,2′-azobis(N,N′-dimethyleneisobutyramidine), free base orhydrochloride, 2,2′-azobis(2-amidinopropane), free base orhydrochloride,2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)ethyl]propionamide} or2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide;acetyl cyclohexane sulphonyl peroxide, diisopropyl peroxy dicarbonate,t-amyl perneodecanoate, t-butyl perneodecanoate, t-butyl perpivalate,t-amylperpivalate, bis(2,4-dichlorobenzoyl)peroxide, diisononanoylperoxide, didecanoyl peroxide, dioctanoyl peroxide, dilauroyl peroxide,bis(2-methylbenzoyl) peroxide, disuccinic acid peroxide, diacetylperoxide, dibenzoyl peroxide, t-butyl per 2-ethylhexanoate,bis-(4-chlorobenzoyl)-peroxide, t-butyl perisobutyrate, t-butylpermaleinate, 1,1-bis(t-butylperoxy)3,5,5-trimethylcyclohexane,1,1-bis(t-butylperoxy)cyclohexane, t-butyl peroxy isopropyl carbonate,t-butyl perisononaoate, 2,5-dimethylhexane 2,5-dibenzoate, t-butylperacetate, t-amyl perbenzoate, t-butyl perbenzoate,2,2-bis(t-butylperoxy) butane, 2,2 bis(t-butylperoxy) propane, dicumylperoxide, 2,5-dimethylhexane-2,5-di-t-butylperoxide, 3-t-butylperoxy3-phenylphthalide, di-t-amyl peroxide, α,α′-bis(t-butylperoxy isopropyl)benzene, 3,5-bis(t-butylperoxy)3,5-dimethyl 1,2-dioxolane, di-t-butylperoxide, 2,5-dimethylhexyne-2,5-di-t-butylperoxide,3,3,6,6,9,9-hexamethyl 1,2,4,5-tetraoxa cyclononane, p-menthanehydroperoxide, pinane hydroperoxide, diisopropylbenzenemono-α-hydroperoxide, cumene hydroperoxide or t-butyl hydroperoxide.

[0121] Azo initiators and peroxides are most preferred.

[0122] Preferably component c) is a compound of formula (IIa), (IIb) or(IIc)

R₃₀—S—H  (IIa),

R₃₀—S—R₃₀  (IIb),

R₃₁—S—S—R₃₁  (IIc)

[0123] wherein R₃₀ is C₁-C₁₈alkyl, C₃-C₁₈ alkenyl, C₃-C₁₈alkinyl,(C₁-C₁₈)alkyl-O—(C₁-C₁₈alkylen)-, HO—(C₁-C₁₈alkylen)-,(C₁-C₁₈alkyl)₂N—(C₁-C₁₈alkylen)-, (C₁-C₁₈)alkyl-O—C(O)—(C₁-C₁₈alkylen)-,phenyl, phenyl(C₁-C₃alkyl), phenyl-C(O)— or (C₁-C₁₈alkyl)₂N—C(S)—; andR₃₁ is C₁-C₁₈alkyl, C₃-C₁₈ alkenyl, C₃-C₁₈alkinyl,(C₁-C₁₈)alkyl-O—(C₁-C₁₈alkylen)-, HO—(C₁-C₁₈alkylen)-.

[0124] Particularly preferred is a compound of formula (IIa), (IIb) or(IIc) wherein R₃₀ and R₃₁ is C₁-C₁₈alkyl.

[0125] Specific compounds are mercaptoethanol, dodecylmercaptane,dibenzylsufide, dibutyl-sulfide, octadecyidisulfide,distearylthiodipropionate (Irganox PS 802),dipalmityldithiodipropionate, dilaurylthiodipropionate (Irganox® PS800).

[0126] More preferably component c) is of formula (IIa) and R₃₀ isC₈-C₁₈alkyl.

[0127] Most preferred is dodecylmercaptane.

[0128] Chain transfer agents are known and for example described in “TheChemistry of Free Radical Polymerization”, Ed. G. Moad, E. Rizzardo,Pergamon 1995, pages 234-251. They are largely items of commerce.

[0129] In contrast to so called “iniferters” (initiator-transferagent-terminator), chain transfer agents are not used alone without aradical initiator. They do not per se suffici ntly initiatepolymerization. A definition and examples for “iniferters” are given byT. Otsu, A. Matsumoto in Adv. Polym. Sci. 1998,136, 75-137.

[0130] A further subject of the invention is a process for preparing anoligomer, a cooligomer, a polymer or a copolymer (block, random orgraft) by free radical polymerization of at least one ethylenicallyunsaturated monomer or oligomer, which comprises (co)polymerizing themonomer or monomers/oligomers in the presence of

[0131] b1) at least one nitroxylether having the structural element

[0132] under reaction conditions capable of effecting scission of theO—X bond to form two free radicals, the radical .X being capable ofinitiating polymerization; or

[0133] b2) at least one stable free nitroxyl radical

[0134] and a free radical initiator and

[0135] c) a chain transfer agent selected from the group consisting of amercaptane, a thioether and a disulfide, with the proviso, that, if astable free nitroxyl radical is present, the chain transfer agent is nota disulfide.

[0136] Also subject of the invention is a process for preparing a block(co)polymer by free radical polymerization which comprises(co)polymerizing

[0137] a) a macroinitiator, which is a oligomer or polymer prepared byradical polymerization in the presence of a nitroxyl radical or anitroxylether and having attached to the oligomer/polymer backbone anitroxyl group with the structural element

[0138] and

[0139] b) an ethylenically unsaturated monomer or oligomer in thepresence of

[0140] c) a chain transfer agent selected from the group consisting of amercaptane, a thioether and a disulfide; under reaction conditionscapable of effecting scission of the O-polymer bond to form two freeradicals, the polymer radical (macroinitiator) being capable ofinitiating polymerization.

[0141] Definitions and preferences for the components have already beengiven above.

[0142] Preferably the nitroxylether of component b1) or the nitroxylradical of component b2) is present in an amount of from 0.001 mol-% to20 mol-%, more preferably of from 0.002 mol-% to 10 mol-% and mostpreferably of from 0.005 mol-% to 5 mol-% based on the monomer ormonomer mixture.

[0143] Preferably the free radical initiator is present in an amount of0.001 mol-% to 20 mol-%, based on the monomer or monomer mixture.

[0144] The molar ratio of free radical initiator to stable free nitroxylradical is preferably from 20:1 to 1:2, more preferably from 10:1 to1:2.

[0145] Scission of the O—X bond or of the O-polymer bond of thenitroxylether or of the macroinitiator may be effected by ultrasonictreatment, radiation with actinic light or heating.

[0146] The scission of the O—X bond or of the O-polymer bond ispreferably effected by heating and takes place at a temperature ofbetween 50° C. and 180° C., more preferably from 80° C. to 145° C.

[0147] Preferably the chain transfer agent, component c), is present inan amount of from 0.001 mol-% to 0,5 mol-%, more preferably of from0.001 mol-% to 0,3 mol-% and most preferably of from 0.001 mol-% to 0,25mol-%, based on the monomer or monomer mixture.

[0148] The molar ratio of stable free nitroxyl radical or nitroxyletherto chain transfer agent is preferably from 100:1 to 4:1.

[0149] After the polymerization step is completed the reaction mixturemay be cooled down to a temperature below 60° C., preferably to roomtemperature. The polymer may be stored at this temperature withoutfurther reactions occuring.

[0150] The process may be carried out in the presence of an organicsolvent or in the presence of water or in mixtures of organic solventsand water. Additional cosolvents or surfactants, such as glycols orammonium salts of fatty acids, may be present. Oth r suitable cosolventsare described hereinafter.

[0151] If organic solvents are used, suitable solvents or mixtures ofsolvents are typically pure alkanes (hexane, heptane, octane,isooctane), aromatic hydrocarbons (benzene, toluene, xylene),halogenated hydrocarbons (chlorobenzene), alkanols (methanol, ethanol,ethylene glycol, ethylene glycol monomethyl ether), esters (ethylacetate, propyl, butyl or hexyl acetate) and ethers (diethyl ether,dibutyl ether, ethylene glycol dimethyl ether), or mixtures thereof.

[0152] The aqueous polymerization reactions can be supplemented with awater-miscible or hydrophilic cosolvent to help ensure that the reactionmixture remains a homogeneous single phase throughout the monomerconversion. Any water-soluble or water-miscible cosolvent may be used,as long as the aqueous solvent medium is effective in providing asolvent system which prevents precipitation or phase separation of thereactants or polymer products until after all polymerization reactionshave been completed. Exemplary cosolvents useful in the presentinvention may be selected from the group consisting of aliphaticalcohols, glycols, ethers, glycol ethers, pyrrolidines, N-alkylpyrrolidinones, N-alkyl pyrrolidones, polyethylene glycols,polypropylene glycols, amides, carboxylic acids and salts thereof,esters, organosulfides, sulfoxides, sulfones, alcohol derivatives,hydroxyether derivatives such as butyl carbitol or cellosolve, aminoalcohols, ketones, and the like, as well as derivatives thereof andmixtures thereof. Specific examples include methanol, ethanol, propanol,dioxane, ethylene glycol, propylene glycol, diethylene glycol,glycerol,dipropylene glycol, tetrahydrofuran, and other water-soluble orwater-miscible materials, and mixtures thereof. When mixtures of waterand water-soluble or water-miscible organic liquids are selected as theaqueous reaction media, the water to cosolvent weight ratio is typicallyin the range of about 100:0 to about 10:90.

[0153] The process is particularly useful for the preparation of blockcopolymers.

[0154] Block copolymers are, for example, block copolymers ofpolystyrene and polyacrylate (e.g., poly(styrene-co-acrylate) orpoly(styrene-co-acrylate-co-styrene). They are useful as adhesives or ascompatibilizers for polymer blends or as polymer toughening agents.Poly(methylmethacrylate-co-acrylate) diblock copolymers orpoly(methylacrylate-co-acrylate-co-methacrylate) triblock copolymers)are useful as dispersing agents for coating systeme, as coatingadditives (e.g. rheological agents, compatibilizers, reactive diluents)or as resin component in coatings(e g. high solid paints). Blockcopolymers of styrene, (meth)acrylates and/or acrylonitrile are usefulas modifiers for plastics, elastomers and adhesives.

[0155] Furthermore, block copolymers of this invention, wherein theblocks alternate between polar monomers and non-polar monomers, areuseful in many applications as amphiphilic surfactants or dispersantsfor preparing highly uniform polymer blends.

[0156] The (co)polymers of the present invention may have a numberaverage molecular weight from 1 000 to 400 000 g/mol, preferably from 2000 to 250 000 g/mol and, more preferably, from 2 000 to 200 000 g/mol.The number average molecular weight may be determined by size exclusionchromatography (SEC), matrix assisted laser desorptonfionization massspectrometry (MALDI-MS) or, if the initiator carries a group which canbe easily distinguished from the monomer(s), by NMR spectroscopy orother conventional methods.

[0157] The polymers or copolymers of the present invention havepreferably a polydispersity of from 1.1 to 2, more preferably of from1.2 to 1.8.

[0158] Thus, the present invention also encompasses in the synthesisnovel block, multi-block, star, gradient, random, hyperbranched anddendritic copolymers, as well as graft copolymers.

[0159] The polymers prepared by the present invention are useful forfollowing applications: adhesives, detergents, dispersants, emulsifiers,surfactants, defoamers, adhesion promoters, corrosion inhibitors,viscosity improvers, lubricants, rheology modifiers, thickeners,crosslinkers, paper treatment, water treatment, electronic materials,paints, coatings, photography, ink materials, imaging materials,superabsorbants, cosmetics, hair products, preservatives, biocidematerials or modifiers for asphalt, leather, textiles, ceramics andwood.

[0160] The following examples illustrate the invention.

[0161] Compounds Used

[0162] The nitroxylether compound (101) and (102) are prepared accordingto GB 2335190

[0163] Compound 102 is the compound of example 7 in GB 2335190. Compound101 is the 4-acetylester of compound 102 and can be prepared fromcompound 101 by standard methods.

[0164] n-butylacrylate and tert.-butylacrylate are commerciallyavailable for example from Merck. 1-dodecylmercaptane andethylhexylthioglycolate are commercially available from Aldrich andWAKO.

EXAMPLES E1 to E3

[0165] In an evacuated Schlenk tube, flushed with argon and equippedwith magnetic stirrer, the amount of nitroxylether and dodecylmercaptanegiven in Table 1 is added to 0.436 mol freshly distilled n-butylacrylateunder an argon atmosphere. The Schlenk tube is closed and the remainingoxygen is removed in two freeze thaw cycles with liquid nitrogen. Thetube is filled with argon and heated to 120° C. for 6 hours withstirring. The remaining monomer is removed under vacuum at roomtemperature. Drying is continued until constant weight of the residue.Molecular weight and distribution are determined using size exclusionchromatography with tetrahydrofurane and calibrated with polystyrenestandards. The results are given in Table 1. TABLE 1 Influence ofdodecylmercaptane on controlled polymerization of n-butylacrylatenitroxylether dodecylmer- (101), mol % captane(mol %) yield sample no.on monomer on monomer (%) M_(n) (calc) M_(n) M_(w) M_(w)/M_(n)comparison V1 1 — 23 3300  3300  4500 1.36 example E1 1 0.1  66 7100 8700 13100 1.5 example E2 1 0.25 85 9100 10500 16800 1.6

[0166] Under the same polymerization conditions a significant increasein yield and molecular weight is observed, whereas the polydispersity(PD) remains low. The slight increase in polydispersity is due to thehigher molecular weights achieved in examples E1 and E2.

[0167] Table 2 shows the result when the nitroxylether is partiallysubstituted by the chain transfer agent. TABELLE 2 Influence of partialsubstitution of the nitroxylether by dodecylmercaptane on controlledpolymerization of n-butylacrylate. nitroxylether dodecylmer- (101), mol% captane(mol %) yield sample no. on monomer on monomer (%) M_(n) (calc)M_(n) M_(w) M_(w)/M_(n) comparison V1 1 — 23  3300  3300  4500 1.36 E30.8 0.2 84 13500 11200 18200 1.62

[0168] A substitution of 20% nitroxylether by dodecylmercaptane leads toa significant increase in yield and polydispersity remains narrow.

[0169] Reinitiating Examples E5 and E6 Using Macroinitiators Prepared inthe Presence of a Nitroxylether and a Chain Transfer Agent

[0170] 2.5 g of the polymers prepared as samples no. V1 and E1 (denotedin the following as macroinitiators, MI) and 7.5 g monomer are added toa Schlenk tube, flushed with argon and equipped with magnetic stirrer.The Schlenck reactor is closed and the remaining oxygen is removed intwo freeze thaw cycles with liquid nitrogen. The tube is filled withargon and heated to 130° C. for 6 hours with stirring. The remainingmonomer is removed under vacuum at room temperature. Drying is continueduntil constant weight of the residue. Molecular weight and distributionare determined using size exclusion chromatography with tetrahydrofuraneand calibrated with polystyrene standards. The results are given inTable 3. TABLE 3 Block copolymerization with n-butylacrylate and styreneyield of added M_(w)/M_(n) monomer monomer sample MI M_(n) (MI) (MI)added (%) M_(n) M_(w) M_(w)/M_(n) comparison V1 3300 1.36 n-butyl- 22 5600  7100 1.27 V2 acrylate E5 E1 8700 1.50 n-butyl- 45 18500 261001.41 acrylate comparison V1 3300 1.35 styrene 57  7800 10900 1.40 V3 E6E1 8700 1.50 styrene 59 20500 28500 1.39

[0171] The results in table 3 clearly show that the polymers(macroinitiators) prepared in the first step in the presence of a chaintransfer agent (example E1) lead to higher yields and higher molecularweights when subjected to a second block copolymerisabon with eithern-butyl-acrylate or styrene as compared to the comparativemacroinitiator (example V1).

EXAMPLES E7-E14

[0172] Polymerization is carried out as described for examples E1-E3using n-butylacrylate and tert.-butylacrylate as monomers and compound102 as nitroxylether. The thiol compound is 1-dodecylmercaptane orethylhexylthioglycolate. The results are shown in Table 4 to 7. TABLE 4Influence of 1-dodecylmercaptane on the controlled polymerization oftert.- butylacrylate nitroxylether thiol compound, mol % on mol % onyield sample no. monomer monomer (%) M_(n) (calc) M_(n) (GPC) M_(w)(GPC) M_(w)/M_(n) comparison 1 — 33 4500 4300  6100 1.4 V4 E7 1 0.1  567500 8400 12400 1.5 E8 1 0.25 67 8900 7600 11800 1.6

[0173] TABLE 5 Influence of ethylhexylthioglycolate on controlledpolymerization of n-butylacrylate nitroxylether thiol compound, mol % onmol % on Yield sample no. monomer monomer (%) M_(n) (calc) M_(n) (GPC)M_(w) (GPC) M_(w)/M_(n) comparison 1 — 32 4300 4300 5400 1.2 V5 E9 10.25 49 6600 6200 8200 1.3 E10 1 0.5  54 7300 6200 8400 1.4

[0174] TABLE 6 Influence of partial substitution of the nitroxylether byethylhexylthioglycolate on controlled polymerization oftert.-butylacrylate nitroxylether thiol compound, mol % on mol % onyield sample no. monomer monomer (%) M_(n) (calc) M_(n) (GPC) M_(w)(GPC) M_(w)/M_(n) comparison 1 — 33  4500  4300  6100 1.4 V4 E11 0.8 0.263 10400  9700 13900 1.4 E12 0.7 0.3 61 11500 10400 14900 1.4

[0175] TABLE 7 Influence of partial substitution of the nitroxylether byethylhexylthioglycolate on controlled polymerization of n-butylacrylatenitroxylether thiol compound, mol % on mol % on yield sample no. monomermonomer (%) M_(n) (calc) M_(n) (GPC) M_(w) (GPC) M_(w)/M_(n) comparison1 — 32  4300  4300  5400 1.2 V5 E13 0.8 0.2 70 11600 11000 13600 1.2 E140.7 0.3 70 13100 10700 15800 1.5

[0176] In both sets of experiments, the replacement of a maximum amoutof 30% (by mol) of nitroxyl ther still allows the controlled radicalpolymerization process to proceed with increased yield accompanied by apolydispersity value as low as measured for the reference sample.

[0177] Reinitiation Experiments Using a Macroinitiator Prepared in thePresence of a Nitroxylether Without the Addition of a Chain TransferAgent (Examples E15-E17). Table 8

[0178] Preparation of the Macroinitiator (V6).

[0179] The macroinitiator (V6) is synthesized using 1 mol %nitroxylether 101 in a 2 L autoclave at 120° C. The monomer,n-butylacrylate, is degassed by applying three consecutivevacuum-argon-flush cycles at room temperature, then the solution isheated rapidly to 120° C. while stirring. The nitroxyl ether, dissolvedin 50 ml of monomer, is added at once when the final reactiontemperature ias reached. The polymerization is allowed to proceed for 6hours. After polymerization the residual monomer is evaporated and thepolymer dried in vacuo at 30° C. until constant weight is achieved. Themacroinitiator V6 is a clear, slightly orange viscous polymer. Theoverall yield is 40%. Molecular weights are analyzed using SECcalibrated with polystyrene standards.

[0180] Reinitiation Experiments

[0181] In a 100 ml Schlenk tube, equipped with a magnetic stir bar, 10 gof V6 are dissolved in 50 g distilled monomer (as listed in the table)until the macroinitiator is completely dissolved. Then, calculatedamounts of 1-dodecylmercaptane are added. Additionally, one experimentin each series is carried out without the thiol as a reference. Thetubes are degassed by three consecutive freeze-thaw-cycles and flushedwith argon. Then they are immersed in an oil bath at 130° C. and thepolymerization is allowed to proceed. After 6 hours, residual monomer isevaporated in vacuo and the polymer obtained dried at 30° C. in vacuountil constant weight is achieved. SEC analysis is performed on thecrude reaction products. TABLE 8 Reinitiation experiments with differentconcentrations of thiol added amount of thiol added (estimation based onC-O-N yield (%) of added endgroups in added sample no. monomermacroinitiaor V6) monomer M_(n) M_(w) M_(w)/M_(n) macroinitiator  5500 7900 1.4 V6 comparison n-butylacrylate 24 12500 15400 1.2 V7 E 15n-butylacrylate 35 mg 69 21700 31000 1.4 E 16 n-butylacrylate 70 mg 7220300 30700 1.5 V 8 tert.- — 16 10600 13300  1.25 butylacrylate E 17tert.- 70 mg 66 18900 26000 1.4 butylacrylate

[0182] From the data obtained it becomes evident that the concept ofadding a chain transfer agent to the controlled polymerization ofvinylic monomers in order to increase yield and molecular weight is notonly valid for a homopolymerization step, but also for any reaction stepin a multi-step polymerization procedure.

[0183] Table 9 shows the results of a second reinitiation step. For theformation of a third subsequent polymerization a polymer listed in Table8 (E 15) was submitted to a consecutive polymerization routine withoutany additional thiol addition. SEC analysis proved the reinitiationability of the polymer.

[0184] Multiple Reinitiation Experiments (Examples E18-E19) Table 9

[0185] 10 grams of the polymer E15 (n-butylacrylate/n-butylacrylate)synthesized in the presence of a chain transfer agent in the secondpolymerization step are added to 50 grams of pure monomer in a Schlenktube, equipped with a magnetic stir bar and dissolved. The tubes aredegassed by three consecutive freeze-thaw-cycles and flushed with argon.Then they are immersed in an oil bath at 130° C. and the polymerizationis allowed to proceed. After 6 hours, residual monomer is evaporated invacuo and the polymer obtained dried at 30° C. in vacuo until constantweight is achieved. SEC analysis is performed on the crude reactionproducts.

[0186] The molecular weight data prove that the third polymerizationstep is successful. Chain extension occurs, whilst maintaining molecularweight control. TABLE 9 Reinitiation experiments using a polymer(macroinitiator) obtained in the presence of a chain transfer agentyield (%) of sample added initial no. Comonomer monomer M_(n) M_(w)M_(w)/M_(n) polymer final polymer E 15 21700 31000 1.4 nBuA-nBuA — E 18n-butylacrylate 37 38700 62200 1.6 nBuA-nBuA nBuA-nBuA- nBuA E 19styrene 64 60400 83700 1.4 nBuA-nBuA nBuA-nBuA-Sty

[0187] Table 10 shows the color improvement of the final product whenpolymerization is carried out in the presence of a chain transfer agent.

[0188] Preparation of comparative example V10 is identical to thepolymerization procedure as described before for n-butylacrylate inexample E1-E3, with the exception that dicumylperoxide is used asinitiator instead of nitroxylether (101) and no dodecylmercaptane isadded. TABLE 10 nitroxylether dodecylmer Yellowness Index Dicumylper-(101), captane 5 measurements and average oxide, mol % mol % (mol %)value of 5 are given sample on monomer on monomer on monomer #1 #2 #3 #4#5 avg. V1 — 1 — 7.27 6.58 6.52 5.32 4.56 6.05 E1 — 1 0.1 4.7 4.41 4.534.42 4.27 4.47 E2 — 1 0.25 3.95 3.7 3.66 3.79 3.57 3.73 E3 — 0.8 0.23.83 3.51 3.61 3.56 3.78 3.66 V10 1 — — 3.47 3.37 3.37 3.44 3.39 3.41

[0189] The results in table 10 show that the Yellowness Index of thepolymers prepared according to the present invention is reduced comparedto the polymer obtained with the nitroxylether alone.

1. A polymerizable composition, comprising a) at least one ethylenicallyunsaturated monomer or oligomer, and b1) at least one nitroxyletherhaving the structural element

,wherein X represents a group having at least one carbon atom and issuch that the free radical X. derived from X is capable of initiatingpolymerization of ethylenically unsaturated monomers; or b2) at leastone stable free nitroxyl radical

and a free radical initiator and c) a chain transfer agent selected fromthe group consisting of a mercaptane, a thioether and a disulfide, withthe proviso, that, if a stable free nitroxyl radical is present, thechain transfer agent is not a disulfide.
 2. A polymerizable composition,comprising a) a macroinitiator, which is a oligomer or polymer preparedby radical polymerization in the presence of a nitroxyl radical or anitroxylether and having attached to the oligomer/polymer backbone anitroxyl group with the structural element

b) an ethylenically unsaturated monomer or oligomer and c) a chaintransfer agent selected from the group consisting of a mercaptane, athioether and a disulfide.
 3. A composition according to claim 1,wherein component b1) is of formula A, B or O,

wherein m is 1, R is hydrogen, C₁-C₁₈alkyl which is uninterrupted orinterrupted by one or more oxygen atoms, cyanoethyl, benzoyl, glycidyl,a monovalent radical of an aliphatic carboxylic acid having 2 to 18carbon atoms, of a cycloaliphatic carboxylic acid having 7 to 15 carbonatoms, or an α,β-unsaturated carboxylic acid having 3 to 5 carbon atomsor of an aromatic carboxylic acid having 7 to 15 carbon atoms; p is 1;R₁₀₁ is C₁-C₁₂alkyl, C₅-C₇cycloalkyl, C₇-C₈aralkyl, C₂-C₁₈alkanoyl,C₃-C₅alkenoyl or benzoyl; R₁₀₂ is C₁-C₁₈alkyl, C₅-C₇cycloalkyl,C₂-C₈alkenyl unsubstituted or substituted by a or cyano, carbonyl orcarbamide group, or is glycidyl, a group of the formula —CH₂CH(OH)—Z orof the formula —CO—Z or —CONH—Z wherein Z is hydrogen, methyl or phenyl;G₆ is hydrogen and G₅ is hydrogen or C₁-C₄alkyl, G₁ and G₃ are methyland G₂ and G₄ are ethyl or propyl or G₁ and G₂ are methyl and G₃ and G₄are ethyl or propyl; and X is selected from the group consisting of—CH₂-phenyl, CH₃CH-phenyl, (CH₃)₂C-phenyl, (C₅-C₆cycloalkyl)₂CCN,(CH₃)₂CCN, —CH₂CH═CH₂, CH₃CH—CH═CH₂ (C₁-C₄alkyl)CR₂₀—C(O)-phenyl,(C₁-C₄)alkyl-CR₂₀—C(O)—(C₁-C₄)alkoxy,(C₁-C₄)alkyl-CR₂₀—C(O)—(C₁-C₄)alkyl,(C₁-C₄)alkyl-CR₂₀—C(O)—N-di(C₁-C₄)alkyl,(C₁-C₄)alkyl-CR₂₀—C(O)—NH(C₁-C₄)alkyl, (C₁-C₄)alkyl-CR₂₀—C(O)—NH₂,wherein R₂₀ is hydrogen or (C₁-C₄)alkyl.
 4. A composition according toclaim 1, wherein component b1) is of formula (Ic), (Id), (Ie), (If),(Ig) or (Ih)

wherein R₁, R₂, R₃ and R₄ independently of each other are C₁-C₁₈alkyl,C₃-C₁₈alkenyl, C₃-C₁₈alkinyl, C₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinylwhich are substituted by OH, halogen or a group —O—C(O)—R₅, C₂-C₁₈alkylwhich is interrupted by at least one O atom and/or NR₅ group,C₃-C₁₂cycloalkyl or C₆-C₁₀aryl or R₁ and R₂ and/or R₃ and R₄ togetherwith the linking carbon atom form a C₃-C₁₂cycloalkyl radical; R₅, R₆ andR₇ independently are hydrogen, C₁-C₁₈alkyl or C₆-C₁₀aryl; R₈ ishydrogen, OH, C₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinyl, C₁-C₁₈alkyl,C₃-C₁₈alkenyl, C₃-C₁₈alkinyl which are substituted by one or more OH,halogen or a group —O—C(O)—R₅, C₂-C₁₈alkyl which is interrupted by atleast one O atom and/or NR₅ group, C₃-C₁₂cycloalkyl or C₆-C₁₀aryl,C₇-C₉phenylalkyl, C₅-C₁₀heteroaryl, —C(O)—C₁-C₁₈alkyl, —O—C₁-C₁₈alkyl orCOOC₁C₁₈alkyl; R₉, R₁₀, R₁₁ and R₁₂ are independently hydrogen, phenylor C₁-C₁₈alkyl; and X is selected from the group consisting of—CH₂-phenyl, CH₃CH-phenyl, (CH₃)₂C-phenyl, (C₅-C₆cycloalkyl)₂CCN,(CH₃)₂CCN, —CH₂CH═CH₂, CH₃CH—CH═CH₂ (C₁-C₄alkyl)CR₂₀—C(O)-phenyl,(C₁-C₄)alkyl-CR₂₀—C(O)—(C₁-C₄)alkoxy,(C₁-C₄)alkyl-CR₂₀—C(O)—(C₁-C₄)alkyl,(C₁-C₄)alkyl-CR₂₀—C(O)—N-di(C₁-C₄)alkyl,(C₁-C₄)alkyl-CR₂₀—C(O)—NH(C₁-C₄)alkyl, (C₁-C₄)alkyl-CR₂₀—C(O)—NH₂,wherein R₂₀ is hydrogen or (C₁-C₄)alkyl.
 5. A composition according toclaim 1, wherein the nitroxyl radical of component b2) is of formula A′,B′ or O′,

wherein m is 1, R is hydrogen, C₁-C₁₈alkyl which is uninterrupted orinterrupted by one or more oxygen atoms, cyanoethyl, benzoyl, glycidyl,a monovalent radical of an aliphatic carboxylic acid having 2 to 18carbon atoms, of a cycloaliphatic carboxylic acid having 7 to 15 carbonatoms, or an α,β-unsaturated carboxylic acid having 3 to 5 carbon atomsor of an aromatic carboxylic acid having 7 to 15 carbon atoms; p is 1;R₁ is C₁-C₁₂alkyl, C₅-C₇cycloalkyl, C₇-C₈aralkyl, C₂-C₁₈alkanoyl,C₃-C₅alkenoyl or benzoyl; R₂ is C₁-C₁₈alkyl, C₅-C₇cycloalkyl,C₂-C₈alkenyl unsubstituted or substituted by a cyano, carbonyl orcarbamide group, or is glycidyl, a group of the formula —CH₂CH(OH)—Z orof the formula —CO—Z or —CONH—Z wherein Z is hydrogen, methyl or phenyl;G₆ is hydrogen and G₅ is hydrogen or C₁-C₄alkyl, and G₁ and G₃ aremethyl and G₂ and G₄ are ethyl or propyl or G₁ and G₂ are methyl and G₃and G₄ are ethyl or propyl.
 6. A composition according to claim 1,wherein the nitroxyl radical of component b2) is of formula (Ic′),(Id′), (Ie′), (If′), (Ig′) or (Ih′)

wherein R₁, R₂, R₃ and R₄ independently of each other are C₁-C₁₈alkyl,C₃-C₁₈alkenyl, C₃-C₁₈alkinyl, C₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinylwhich are substituted by OH, halogen or a group —O—C(O)—R₅, C₂-C₁₈alkylwhich is interrupted by at least one O atom and/or NR₅ group,C₃-C₁₂cycloalkyl or C₆-C₁₀aryl or R₁ and R₂ and/or R₃ and R4 togetherwith the linking carbon atom form a C₃-C₁₂cycloalkyl radical; R₅, R₆ andR₇ independently are hydrogen, C₁-C₁₈alkyl or C₆-C₁₀aryl; R₈ ishydrogen, OH, C₁-C₁₈alkyl, C₃-C₁₈alkenyl, C₃-C₁₈alkinyl, C₁-C₁₈alkyl,C₃-C₁₈alkenyl, C₃-C₁₈alkinyl which are substituted by one or more OH,halogen or a group —O—C(O)—R₅, C₂-C₁₈alkyl which is interrupted by atleast one O atom and/or NR₅ group, C₃-C₁₂cycloalkyl or C₆-C₁₀aryl,C₇-C₉phenylalkyl, C₅-C₁₀heteroaryl, —C(O)—C₁-C₁₈alkyl, —O—C₁-C₁₈alkyl or—COOC₁-C₁₈alkyl; and R₉, R₁₀, R₁₁ and R₁₂ are independently hydrogen,phenyl or C₁-C₁₈alkyl.
 7. A composition according to claim 2 wherein thestructural element

of the macroinitiator is derived from a compound of formulae A, B, O(A′, B′, O′) according to claim 3 or of formulae Ic, Id, Ie, If, Ig, Ih(Ic′, Id′, Ie′, If′, Ig′, Ih′) according to claim
 4. 8. A compositionaccording to claim 1 or 2, wherein component c) is a compound of formula(IIa), (IIb) or (IIc) R₃₀—S—H  (IIa),R₃₀—S—R₃₀  (IIb),R₃₁—S—S—R₃₁  (IIc)wherein R₃₀ is C₁-C₁₈alkyl, C₃-C₁₈ alkenyl, C₃-C₁₈alkinyl,(C₁-C₁₈)alkyl-O—(C₁-C₁₈alkylen)-, HO—(C₁-C₁₈alkylen)-,(C₁-C₁₈alkyl)₂N—(C₁-C₁₈alkylen)-, (C₁-C₁₈)alkyl-O—C(O)—(C₁-C₁₈alkylen)-,phenyl, phenyl(C₁-C₃alkyl), phenyl-C(O)— or (C₁-C₁₈alkyl)₂N—C(S)—; andR₃₁ is C₁-C₁₈alkyl, C₃-C₁₈ alkenyl, C₃-C₁₈alkinyl,(C₁-C₁₈)alkyl-O—(C₁-C₁₈alkylen)-, HO—(C₁-C₁₈alkylen)-.
 9. A compositionaccording to claim 8, wherein component c) is of formula (IIa) and R₃₀is C₈-C₁₈alkyl.
 10. A process for preparing an oligomer, a cooligomer, apolymer or a copolymer (block, random or graft) by free radicalpolymerization of at least one ethylenically unsaturated monomer oroligomer, which comprises (co)polymerizing the monomer ormonomers/oligomers in the presence of b1) at least one nitroxyletherhaving the structural element

under reaction conditions capable of effecting scission of the O—X bondto form two free radicals, the radical .X being capable of initiatingpolymerization; or b2) at least one stable free nitroxyl radical

and a free radical initiator and c) a chain transfer agent selected fromthe group consisting of a mercaptane, a thioether and a disulfide, withthe proviso, that, if a stable free nitroxyl radical is present, thechain transfer agent is not a disulfide.
 11. A process for preparing ablock (co)polymer by free radical polymerization which comprises(co)polymerizing a) a macroinitiator, which is a oligomer or polymerprepared by radical polymerization in the presence of a nitroxyl radicalor a nitroxylether and having attached to the oligomer/polymer backbonea nitroxyl group with the structural element

b) an ethylenically unsaturated monomer or oligomer in the presence ofc) a chain transfer agent selected from the group consisting of amercaptane, a thioether and a disulfide; under reaction conditionscapable of effecting scission of the O-polymer bond to form two freeradicals, the polymer radical (macroinitiator) being capable ofinitiating polymerization.
 12. A process according to claim 10, whereinthe nitroxylether of component b1) or the nitroxyl radical of componentb2) is present in an amount of from 0.001 mol-% to 20 mol-%, based onthe monomer or monomer mixture.
 13. A process according to claim 10,wherein the free radical initiator is present in an amount of 0.001mol-% to 20 mol-%, based on the monomer or monomer mixture.
 14. Aprocess according to claim 10 or 11, wherein the scission of the O—Xbond or the scission of the O-polymer bond is effected by heating andtakes place at a temperature of between 50° C. and 180° C.
 15. A processaccording to claim 10 or 11, wherein the chain transfer agent, componentc), is present in an amount of from 0.001 mol-% to 0,5 mol-%, based onthe monomer or monomer mixture.
 16. Use of a chain transfer agentselected from the group consisting of a mercaptane, a thioether and adisulfide for increasing rate and yield of controlled radicalpolymerizations in the presence of a nitroxylether

a stable free nitroxyl radical

and a free radical initiator, with the proviso, that, if a stable freenitroxyl radical is present, the chain transfer agent is not adisulfide.